Film forming apparatus and film forming method

ABSTRACT

A film forming apparatus is provided which includes a device A that generates liquid fine particles having controlled particle diameters; a device B including a via for guiding the generated liquid fine particles while controlling a temperature thereof; a device C that sprays the guided liquid fine particles; and a device D including a space for forming a transparent conductive film by coating the sprayed liquid fine particles onto a subject to be processed.

This is a divisional of application Ser. No. 12/046,963, filed Mar. 12,2008 which claims priority from Japanese Patent Application No.2005-265301, filed Sep. 13, 2005, the contents of which are incorporatedherein by reference.

TECHNICAL FIELD

Apparatuses and methods consistent with the present invention relate toa film forming apparatus and a film forming method that are suitablyused when a transparent conductive film or the like is being formed on abase material using a spray pyrolysis deposition (SPD) method, and thatmake it possible to spray droplets whose particle diameters have beenmade uniform in advance.

BACKGROUND ART

In solar cells, liquid crystal display (LCD) units, plasma display (PDP)units and the like of the related art, a base material with atransparent conductive film (TCF) that is obtained by forming thetransparent conductive film on the transparent base material that isformed, for example, from glass or the like that is a non-conductivebody is widely used.

These transparent conductive films are films whose main constituent is aconductive metallic oxide such as indium tin oxide (ITO), tin oxide(TO), and fluorine-doped tin oxide (FTO), and have a combination ofexcellent transparency to visible light and excellent electricalconductivity. Among these transparent conductive films, transparentconductive films having indium tin oxide (ITO), in particular, as theirmain constituent are widely known, and these are used in the liquidcrystal display (LCD) units for personal computers (PC), televisions,and mobile telephones and the like.

One method of forming a transparent conductive film such as indium tinoxide (ITO) on a transparent base material is spray pyrolysis deposition(SPD).

This spray pyrolysis deposition is a technology involving a series ofreactions. In this technology, a solution constituting a raw material issprayed using a spraying device such as an atomizer onto a base materialthat has been preheated to a film formation temperature. In the initialstages of the resulting reaction, crystals are formed as a result of avaporization of the solvent contained in the droplets that have beendeposited on the surface of the base material and a reaction of solutesin the droplets. As the reaction progresses, droplets adhere onto thecrystals (i.e., a polycrystalline substance) that have formed on thebase material, and, as a result of a vaporization of the solvent in thedroplets and a progress of the reaction between the solutes and thecrystals underneath, crystalline (i.e., a polycrystalline substance)growth progresses.

In this spray pyrolysis deposition, an aqueous solution or alcoholsolution of a metal inorganic salt, or an organic solution obtained bydissolving an organic metal compound or organic acid-base in an organicsolvent, or a mixed solution obtained by mixing these solutions, or thelike is used as the favorable raw material solution to be sprayed. Thetemperature of the base material differs depending on the type ofstarting material or raw material solution, however, the temperaturerange is set to 250 to 700° C. Because the film forming apparatus usedin this type of spray pyrolysis deposition is simple and low in cost, itis effective when forming transparent conductive films at low cost.

A transparent conductive film (TCO: transparent conductive oxide) isglass that has been provided with conductivity by forming a thin film ofa semiconductor ceramic such as tin-doped indium oxide (ITO), tin oxide(TO), or fluorine-doped tin oxide (FTO) on the surface of non-conductiveglass, and has the property of conducting electricity in spite of beingtransparent. Among these, ITO, in particular, is widely known as atransparent conductive film and is used in the liquid crystal displayunits of personal computers, televisions, and mobile telephones and thelike.

Using spray pyrolysis deposition, it is possible to form a transparentconductive film or the like at low cost because the film formingapparatus is simple and the raw material is also comparatively low incost. An aqueous solution or alcohol solution of a metal inorganic salt,or an organic metal compound or organic solvent based solution of anorganic acid-base is used for the starting material of the transparentconductive film. The temperature of the substrate differs depending onthe starting material or raw material solution, however, the temperaturerange is set to 250 to 700° C.

However, in a related art film forming apparatus 1100 that includes aliquid supply component 1120 and a vapor supply component 1121 such asis shown in FIG. 1, in a fine particle formation device a, liquid thatis supplied from the liquid supply component 1120 and vapor that issupplied from the vapor supply component 1121 are made to collide witheach other so that the raw material solution formed by the two ischanged into fine particles. When the raw material in fine particle formis sprayed onto a base material 1110 by a spray device c, the size ofdroplets 1122 that are sprayed from the spray device c is dependent onthe spray nozzles (may also be hereinafter referred to as two-fluidspray nozzles) in the spray device c, and it is difficult to obtain auniform size in the droplets 1122 which causes the film thickness to beuneven. Namely, in the preparation of a transparent conductive filmusing spray pyrolysis deposition inside a transparent conductive filmforming device, when spray nozzles are used to spray a raw materialsolution onto a base material that has been heated to a temperaturerange of 250 to 700° C., the droplets 1122 that are sprayed from thespray nozzles have a size distribution of between 10 μm and 120 μm, asis shown by the related art apparatus in FIG. 6, even when two-fluidspray nozzles that allow fine particles to be formed are used. As aresult, when forming a film over a large surface area, in-planedistribution ends up being generated in the sprayed droplets (i.e.,mist) so that film thickness distribution is increased and aconsiderably high distribution is created in some film characteristics,such as sheet resistance and transmissivity.

Therefore, several devices have been proposed as devices to make thesize of the sprayed droplets uniform. For example, it has been observedthat, among droplets sprayed from spray nozzles, droplets having a largeparticle diameter are present in greater numbers at positions away fromthe center of the spray path. It has also been observed that coarsedroplets contained in the vicinity of the center have a fast spray speedand fly further than fine droplets. Accordingly, technology has beenproposed in which wall surfaces are provided at a front surface andsurrounding the spray path so that droplets having a large particlediameter that fly to positions away from the center of the spray pathand coarse droplets that fly far from the vicinity of the center collidewith these wall surfaces and are removed (see Japanese Unexamined PatentApplication, First Publication No. H05-320919 and Japanese UnexaminedPatent Application, First Publication No. 2001-205151).

However, the above described devices attempt to make the size of thedroplets uniform by efficiently selecting sprayed droplets, and do notspray droplets whose particle sizes have already been made uniform inadvance. Accordingly, there is a limit as to how uniform the size of thedroplets can be made and it is difficult to use only fine droplets toform a film.

Moreover, it is necessary for a sufficient distance, for example,approximately 500 mm to be provided between the discharged spray and thebase material. This makes positive temperature control as well ascontrol of the droplet spray speed and of the force of their collisionwith the base material impossible. As a result, film formation in whichthe film characteristics are precisely controlled has not been possible.

Another example of a related film forming apparatus that uses spraypyrolysis deposition is shown in FIG. 2. This film forming apparatus2100 comprises a supporting device 2120 on which a substrate 2110 ismounted and with a discharge device 2130 that sprays a raw materialsolution in spray form. The supporting device 2120 has a heating deviceembedded therein that heats a mounted substrate to a predeterminedtemperature (see, for example, Japanese Unexamined Patent Application,First Publication No. H06-012446).

In order to spray mist uniformly onto a substrate having a large surfacearea at an angle of, for example, 200 mm or more, it is necessary toarrange and drive a large number of mist spray nozzles.

However, if mist is sprayed using related art circular nozzles (i.e.,60φ mm), then as is shown in FIGS. 3A and 3B, if the nozzles are drivenin a circular shape or, as is shown in FIGS. 4A and 4B, if the nozzlesare driven in an elliptical shape, the distribution is increased in thesprayed quantity of the mist. In order to reduce the effects of thisdistribution, it has been necessary to conduct even more complex drivecontrol.

SUMMARY OF THE INVENTION

It is an exemplary object of the present invention to provide a filmforming apparatus and a film forming method that make it possible tospray droplets whose particle diameters have been made uniform inadvance.

It is a further exemplary object of the present invention to provide afilm forming apparatus and a film forming method that make it possibleto spray mist uniformly over a substrate having a large surface area andto make the thickness of the formed film uniform.

Exemplary embodiments of the present invention address the objectsdescribed above and other objects not described. Also, the presentinvention is not required to address the above-described objects.

Exemplary embodiments of the present invention provide the followingfilm forming apparatus and film forming method that employ spraypyrolysis deposition.

Namely, a film forming apparatus that uses spray pyrolysis depositionaccording to a first aspect of the present invention includes: a deviceA that generates liquid fine particles, the liquid fine particles havingcontrolled particle diameters; a device B that is defined by a space forguiding the generated liquid fine particles while controlling atemperature thereof; a device C that sprays the guided liquid fineparticles; and a device D that is defined by a space for forming atransparent conductive film by coating the sprayed liquid fine particlesonto a subject to be processed.

In this film formation apparatus that uses spray pyrolysis deposition astructure is employed in which, in the device A, liquid fine particlesare generated whose particle diameters have been made uniform in advanceby controlling the particle diameter of sprayed droplets. Next, in thedevice B, only liquid fine particles whose particles diameters have beenmade uniform are transported to the device C. Thereafter, in the deviceC, only minute liquid fine particles whose particle diameters havealready been made uniform are sprayed onto a base material (i.e., asubject to be processed) that is placed in the space of the device D.

As a result, it is possible to form a film that has little unevenness inthe film thickness.

In a film forming apparatus that uses spray pyrolysis depositionaccording to a second aspect of the present invention, in the device B,the space for guiding the liquid fine particles may be isolated from theoutside by a partitioning member that has water repellency or has aninternal surface that is undergone water repellency treatment. Waterrepellency may be achieved by providing a coating film that is suitablefor imparting water repellency, such as Teflon® resin or a vinylchloride resin or the like, and providing conditions of a contact angleof 80° or more for the contact between the liquid fine particles and theinterior wall of the delivery path that transports the liquid fineparticles while guiding them.

By employing this type of structure, it is possible to reduce effectsfrom the outside temperature while suppressing adhesion of the liquidfine particles to the partitioning plate.

In a film forming apparatus that uses spray pyrolysis depositionaccording to a third aspect of the present invention, in the device B,it is also possible for the space for guiding the liquid fine particlesto be isolated from the outside by a partitioning member and to have amechanism that performs temperature control such that a temperatureinside the space is kept at a higher temperature than the outside.

By employing this type of structure, adhesion of liquid fine droplets tothe interior wall of the delivery path due to condensation or the likeand a bonding together of the liquid fine particles can be suppressed sothat it is possible to supply, stably, liquid fine particles whoseparticle diameters have been made uniform to the device C.

A film forming apparatus according to a fourth aspect of the presentinvention is a film forming apparatus that forms a thin film on asurface of a subject to be processed by spray pyrolysis deposition andincludes: a supporting device on which the subject to be processed ismounted; and a discharging device that sprays a mist containing a rawmaterial solution for the thin film towards a surface of the subject tobe processed, wherein the discharge device comprises nozzles, eachnozzle having a first position that forms a mist intake side and asecond position that forms a mist discharge side, and if a face velocityat the first position is taken as V₁ and a face velocity at the secondposition is taken as V₂, a face velocity of the mist moving through thenozzles is V₂>1.5×V₁.

In a film forming apparatus according to a fifth aspect of the presentinvention, in the above described film forming apparatus 1, in thenozzles, if a cross-sectional area of the first portion when seen fromthe discharge aperture side is taken as E₁ and a cross-sectional area ofthe second portion is taken as E₂, E₁>1.5×E₂.

In a film forming apparatus according to a sixth aspect of the presentinvention, in the above described film forming apparatus, the shape ofthe nozzles at the second position is a slit shape.

In a film forming apparatus according to a seventh aspect of the presentinvention, in the above described film forming apparatus, there arefurther provided: a preparation chamber where the mist is generated byspraying in advance the raw material solution; and a transporting devicethat is defined by a space that enables the mist to move from thepreparation chamber to the nozzles.

In a film forming apparatus according to an eighth aspect of the presentinvention, in the above described film forming apparatus, during filmformation the nozzles are shifted in a horizontal direction relative toa surface of the subject to be processed.

In a film forming apparatus according to a ninth aspect of the presentinvention, in the above described film forming apparatus, if themovement in a horizontal direction of the nozzles is a reciprocatingmovement, then in a vicinity of a turn portion, the nozzles are shiftedin a direction in which they move away from the surface of the subjectto be processed.

A film forming method according to a tenth aspect of the presentinvention is a film forming method for forming a film on a base materialby spray pyrolysis deposition that includes: generating liquid fineparticles having controlled particle diameters; performing temperaturecontrol on generated liquid fine particles and guiding them with theparticle diameters thereof made uniform; spraying the guided liquid fineparticles; and forming a film by causing the sprayed liquid fineparticles to accumulate on the base material.

As a result of the above, because it is possible to form a film usingonly liquid fine particles whose particle diameters have been madeprecisely uniform, it is possible to form a film having little filmthickness distribution.

According to the film forming apparatus that uses spray pyrolysisdeposition of an exemplary embodiment of the present invention, byintroducing liquid fine particles, whose particle diameters arecontrolled, via a space that guides them while controlling theirtemperature to nozzles serving as a spraying device, it becomes possiblefor the in-plane distribution of the liquid fine particles that aresprayed from the nozzles to be made uniform, and the in-planedistribution range of the film characteristics can be contracted (i.e.,narrowed).

Consequently, a film forming apparatus according to an exemplaryembodiment of the present invention contributes to fields in which atransparent conductive film having a large surface area is required, forexample, fields such as liquid crystal display devices and EL displaydevices.

In an exemplary film forming method of the present invention, because atransparent conductive film is formed using liquid fine particles whoseparticle diameters have been made uniform, it becomes possible to form auniform and homogeneous film irrespectively of the surface area of thebase material (i.e., the subject to be processed).

Consequently, the construction of a production system that produces, inlarge quantities, transparent conductive films having a large surfacearea is possible.

According to an exemplary embodiment of the present invention, ifnozzles are provided in a discharge device that sprays mist that isformed by the raw material solution of a thin film, by stipulating thata relationship between a face velocity V₁ of the mist at a firstposition and a face velocity V₂ of the mist at a second position satisfyV₂>1.5×V₁, it becomes possible to provide a film forming apparatus thatis capable of achieving a uniform spray amount over the entire surfaceof a subject to be processed and of achieving an improvement in the filmformation speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the structure of a related art filmforming apparatus.

FIG. 2 is a view schematically showing an example of a related art filmforming apparatus.

FIG. 3A is a view showing a nozzle driving pattern and a sprayed mistdistribution.

FIG. 3B is a view showing a nozzle driving pattern and a sprayed mistdistribution.

FIG. 4A is a view showing a nozzle driving pattern and a sprayed mistdistribution.

FIG. 4B is a view showing a nozzle driving pattern and a sprayed mistdistribution.

FIG. 5 is a schematic view showing the structure of an example of a filmforming apparatus of an exemplary embodiment of the present invention.

FIG. 6 is a view showing a size distribution of fine particles in liquidform controlled by a film forming apparatus of an exemplary embodimentof the present invention as compared with a conventional apparatus.

FIG. 7 is a view schematically showing another example of a film formingapparatus of an exemplary embodiment of the present invention.

FIG. 8 is a view showing the nozzles shown in FIG. 7.

FIG. 9 is a view showing a nozzle driving pattern and a sprayed mistdistribution.

FIG. 10 is a view showing a nozzle driving pattern and a sprayed mistdistribution.

FIG. 11 is a view showing a placement and driving of nozzles.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

A first exemplary embodiment of the present invention will now bedescribed.

FIG. 5 is a schematic view showing a structure of a film formingapparatus according to the present embodiment.

A film forming apparatus 11 according to the present embodimentcomprises a device A (hereinafter referred to as a “liquid fine particlegenerating device”) that generates first liquid fine particles whoseparticle diameter is controlled, a device B (hereinafter referred to asa “liquid fine particle guiding device”) that is defined by a space thatguides the generated first liquid fine particles while performingtemperature control thereof, a device C (hereinafter referred to as a“liquid fine particle spraying device”) that converts the guided firstliquid fine particles into finer second liquid fine particles 12 andthen sprays these, and a device D (hereinafter referred to as a“transparent conductive film forming device”) that is defined by a spacethat makes the sprayed second liquid fine particles 12 coated onto asubject to be processed (i.e., base material) in the form of a glasssubstrate 110 so as to form a transparent conductive film.

The liquid fine particle generating device A controls droplets that havebeen sprayed preliminarily using a spray device that is different fromthe liquid fine particle spraying device C (described below) so as tomake a selection such that only droplets having a small diameter (i.e.,fine droplets) are efficiently extracted as first liquid fine particlesso that the size thereof is made uniform.

The generated first liquid fine particles may contain between 60.0% byvolume and 98.8% by volume of air.

The liquid fine particles guiding device B has a delivery path in theform of a space where the first liquid fine particles that weregenerated with a controlled particle diameter by the liquid fineparticle generating device A are transported while being guided suchthat there is no damage to the particle diameter from the liquid fineparticle generating device A as far as the subsequent liquid fineparticle spraying device C.

This delivery path is isolated from the outside by a partitioningmember, and is controlled such that the temperature of the interiorwalls is the same as or higher than that of the liquid fine particles.In addition, the temperature thereof is maintained such that theevaporation rate of the solvent in the transparent conductive film rawmaterial solution does not become excessive. Namely, such that arelationship is established whereby the liquid fine particletemperature>delivery path internal wall temperature>solvent evaporationtemperature.

In addition, a flow having a flow rate of between 100 cm/min and 100,000cm/min is present in the liquid fine particles inside the delivery.

Moreover, the interior walls of the delivery path are isolated from theoutside by using a material having water repellency such as afluororesin or the like, or by performing processing to impart waterrepellency to the surfaces thereof. At this time, if a material havingexcellent heat propagation properties such as a metal is used for thedelivery, then it is easily affected by the outside temperature and maylead to liquid fine particles adhering to the interior walls of thedelivery. Because of this, a resin material having low heat propagationsuch as a vinyl chloride resin or a fluororesin or the like may be used.Note that if a metal material is used, this can be addressed byperforming temperature control on the outside walls of the delivery.

Moreover, if hydrochloric acid, sulfuric acid, or nitric acid is usedfor the chemical solution, then it is necessary to use a material havingchemical resistant properties for the interior walls that are in directcontact with the liquid fine particles, or to perform surface treatmentthereon using a material having chemical resistant properties.

Furthermore, the distance of the delivery path may be short. However, itis also possible to think of cases when some distance is required fromthe viewpoint of design such as restrictions imposed by the temperatureof the liquid fine particles and the temperature of the interior walls,and the placement from various devices. When this distance is increased,it may be less than 10 meters.

The liquid fine particle spray device C sprays liquid fine particlesthat have been guided by the liquid fine particle guiding device B ontothe glass substrate 110 that is placed in the space of the subsequenttransparent conductive film forming device D. Liquid fine particles aresprayed at a flow rate of between 1,000 cm/min and 100,000 cm/min from adischarge aperture in the liquid fine particle spraying device C. Thedistance between the discharge aperture in the liquid fine particlespraying device C and the surface of the glass substrate 110 iscontrolled so as to be between 5 mm and 200 mm.

The transparent conductive film forming device D is positioned facingthe discharge aperture in the liquid fine particle spraying device C andcomprises a space for mounting the glass substrate 110 on which theliquid fine particles that form a transparent conductive film aredeposited. In the transparent conductive film forming device D, a rawmaterial solution for a transparent conductive film that containsconductive polymers that have been sprayed onto the glass substrate 110is coated so as to form an initial layer of the transparent conductivefilm.

The surface of the glass substrate 110 is heated by heat transfer from asubstrate heater located beneath it, heat ray irradiation from a heatray heater located above it, and by a high temperature flow from anupper atmosphere, so that the temperature range is controlled to between200° C. and 600° C.

Next, the film forming method for forming the transparent conductivefilm according to the present embodiment will be described.

Firstly, liquid fine particles whose particle diameter is controlled bythe liquid particle generating device A are generated. Next, thetemperature of the generated liquid fine particles is controlled by theliquid fine particle guiding device B and the liquid fine particleshaving uniform particle diameters are guided to the liquid fine particlespraying device C. Thereafter, the guided liquid fine particles aresprayed onto a subject to be processed by the liquid fine particlespraying device C and the liquid fine particles 12 that have beensprayed in the transparent conductive film forming device D aredeposited on the glass substrate 110 that is serving as a subject to beprocessed so that a film is formed.

The film forming apparatus according to a second exemplary embodiment ofthe present invention will now be described based on the drawings.

FIG. 7 is a view schematically showing a film forming apparatusaccording to the second embodiment of the present invention

A film forming apparatus 21 is a film forming apparatus that forms athin film on a subject 22 to be processed by spray pyrolysis depositionand includes a supporting device 211 on which the subject to beprocessed 22 is mounted, and a discharging device 212 that sprays a mist23 that is formed from a raw material solution for the thin film onto asurface of the subject 22 to be processed.

Moreover, in a film forming apparatus 21 of this embodiment, the nozzleprovided in the discharge device 212 has a first portion 212 a thatforms the mist intake side and a second portion 212 b that forms themist discharge side, and a third portion 212 c. Regarding the facevelocity of mist moving through the nozzle, the face velocity V₁ in thefirst portion 212 a and the face velocity V₂ of the second portion 212 bare set so as to satisfy the following formula.

V ₂>1.5×V ₁  (1)

By regulating the face velocity V₁ of the mist in the first portion 212a and the face velocity V₂ of the mist in the second portion 212 b inthe manner described above, the sprayed mist quantity over the entiresurface of the subject 22 to be processed is made uniform and the filmformation rate can be increased.

The supporting device 211 has a temperature control device embeddedtherein that includes functions of heating, maintaining the temperatureof, and cooling the subject 22 to be processed in order to form a thinfilm while keeping the surface of the subject 22 to be processed onwhich a film is being formed at a predetermined temperature. Thetemperature control device is, for example, a heater.

The discharge device 212 sprays mist 23 onto the subject 22 to beprocessed that is placed in a space in a film formation chamber 210. Themist 23 is sprayed at a flow rate of between 100 cm/min and 100,000cm/min from the discharge aperture of the discharge device 212. Thedistance between the discharge device 212 and the surface of the subjectto be processed 2 is controlled between 5 mm and 200 mm.

The discharge device 212 is, for example, a nozzle. Moreover, the rawmaterial solution that is sprayed from the discharge device 212 is themist 23 (i.e., liquid fine particles).

This mist 23 may also be generated by spraying raw material solution inadvance in a preparation chamber 220 (described below).

In addition, the surface of the subject 22 to be processed is heated byheat transfer or the like from the temperature control device, and thetemperature range is controlled to between 200° C. and 600° C.

In the film forming apparatus 21 of the present invention, in the nozzleprovided in the discharge device 212, when viewed from the dischargeaperture side a cross-sectional area E₁ of the first portion 212 a and across-sectional area E₂ of the second portion 212 b are set so as tosatisfy the following formula.

E ₁>1.5×E ₂  (2)

In the nozzle, by regulating the cross-sectional area E₁ of the firstportion 212 a and the cross-sectional area E₂ of the second portion 212b in the above manner, the face velocity of the mist moving inside thenozzle can be easily changed between the first portion 212 a and thesecond portion 212 b. Note that the cross-sectional areas E₁ and E₂ arethe cross-sectional areas of the nozzle internal dimension.

Specifically, a relationship between the mist face velocity V₁ in thefirst portion 212 a and the mist face velocity V₂ in the second portion212 b can be set to V₂>1.5×V₁.

The first portion 212 a may be circular and the second portion 212 b maybe slit-shaped. By making the second portion 212 b that forms thedischarge aperture slit-shaped, mist can be sprayed uniformly even ontoa subject to be processed that has a large surface area so that a filmcan be formed uniformly.

Furthermore, in a slit-shaped discharge aperture, as is shown in FIG. 8,the nozzle shape is designed such that no difference is generatedbetween the mist flow rate in a center portion and the mist flow rate atend portions. FIG. 8 is an view of a nozzle portion.

As is shown in FIG. 8, an inner diameter H of the first portion 212 a(i.e., a cylindrical portion), a length X and a width Y of the apertureportion of the second portion 212 b (i.e., a slit portion), a length Gof the second portion 212 b, and a length F of a third portion (i.e., aconstricted portion) that connects the first portion 212 a to the secondportion 212 b are set so as to satisfy the following formula.

(X−H)<2.5×F (F≦G)  (3)

By designing the nozzle shape such that Formula (3) is satisfied, themist flow rate in a slit-shaped discharge aperture can be made equal ina center portion and at end portions, and mist can be sprayed uniformlyonto the subject 22 to be processed.

Moreover, during film formation, the nozzle is moved in a horizontaldirection along one surface of the subject 22 to be processed. By movingthe nozzle, a film can be formed uniformly even on a subject to beprocessed that has a large surface area.

At this time, by making the movement of the nozzle in a horizontaldirection a reciprocating movement, it becomes possible to form a filmon a subject to be processed that has a larger surface area, however, asis shown in FIG. 9, there is a tendency for the spray quantitydistribution to become concentrated in driving turning portions (i.e.,in turn portions). This is because it is difficult to control the nozzleduring turning. Namely, at the stage when nozzle turn control is begun,the nozzle shift speed is decreased so that the spray quantity in theseareas increases.

Therefore, in order to avoid the sprayed mist quantity becomingconcentrated in turn portions, at the stage when nozzle turn control isbegun, the spray height of the nozzle may be controlled proportionallyas the nozzle shift speed is decreased.

Namely, in the film forming apparatus 21, if the movement of the nozzlein a horizontal direction is a reciprocating movement, then as is shownin FIG. 10, in the vicinity of the turn portions the nozzle is moved ina direction in which it moves away from a surface of the subject 22 tobe processed.

In end portions of the subject 22 to be processed which form turnportions in a reciprocating movement, by performing film formation whileraising the height of the nozzle from the surface of the subject 22 tobe processed, the sprayed mist quantity can be made uniform over theentire surface of the subject 22 to be processed. As a result, it ispossible to reduce any unevenness in the film thickness of a formed thinfilm.

Moreover, this film forming apparatus 21 is further provided with apreparation chamber 220 that generates the mist 23 by spraying a rawmaterial solution in advance, and a transporting device that is definedby a space and moves the mist 23 from the preparation chamber 220 to thedischarge device 212.

In the preparation chamber 220, the raw material solution is sprayed inadvance using a spraying device that is different from the abovedescribed spraying device 212 and control is performed to make aselection such that only droplets having a small diameter (i.e., fine)are efficiently extracted as the mist 23 so that the size thereof ismade uniform. Because a finer mist can be sprayed a film having goodcharacteristics can be formed.

The generated mist 23 may contain between 60.0% by volume and 98.8% byvolume of air.

The transporting device has a delivery path 221 in the form of a spacewhere the generated mist 23 is transported while being guided.

The delivery path 221 is isolated from the outside by a partitioningmember, and is controlled such that the temperature of the interiorwalls is the same as or higher than that of the mist 23. In addition,the temperature thereof is maintained such that the evaporation rate ofthe solvent in the raw material solution does not become excessive.Namely, a relationship whereby the mist 23 temperature>delivery path 221internal wall temperature>solvent evaporation temperature.

In addition, a flow having a flow rate of between 100 cm/min and 100,000cm/min is present in the mist 23 inside the delivery path 221.

Moreover, the interior walls of the delivery path 221 are isolated fromthe outside by using a material having water repellency such as afluororesin or the like, or by performing processing to impart waterrepellency to the surfaces thereof. At this time, if a material havingexcellent heat propagation properties such as a metal is used for thedelivery path 221, then it is easily affected by the outside temperatureand may lead to the mist 23 adhering to the interior walls of thedelivery. Because of this, a resin material having low heat propagationsuch as a vinyl chloride resin or a fluororesin or the like may be used.Note that if a metal material is used, this can be addressed byperforming temperature control on the outside walls of the delivery.

Moreover, if a chemical solution, such as hydrochloric acid, sulfuricacid, or nitric acid, is used, then it is necessary to use a materialhaving chemical resistant properties for the interior walls that are indirect contact with the mist 23, or to perform surface treatment thereonusing a material having chemical resistant properties.

Furthermore, the distance of the delivery path 221 may be short.However, it is also possible to think of cases when some distance isrequired from the viewpoint of design such as restrictions imposed bythe temperature of the liquid fine particles and the temperature of theinterior walls, and the placement from various devices. When thisdistance is increased, it may be less than 10 meters.

Moreover, in this film forming chamber, a space that includes thesubject 22 may be processed and the discharge device 212 may be enclosedin a hood 214.

The hood 214 is formed from a non-corrosive metal such as stainlesssteel. Aperture portions are formed on both sides in the vicinity of thebottom portion.

In the film forming apparatus 21, because the hood 214 is positioned soas to enclose the space between the discharge device 212 and the subject22 to be processed that is placed in a position facing the dischargedevice 212, raw material solution that is discharged in spray form fromthe discharge aperture of the discharge device 212 is not affected bythe outside air, and a state can be stably maintained in which the rawmaterial solution is sprayed from the discharge aperture into a radialspace in the direction of the subject 22 to be processed. In otherwords, the hood 214 also helps to prevent raw material solutionscattering from the space inside the hood 214 to the outside of theapparatus and causing an unnecessary increase in the amount used. As aresult, the raw material solution is used effectively to form a thinfilm.

Moreover, because the hood 214 is positioned so as to enclose the spacebetween the discharge device 212 and the subject 22 to be processed,during film formation, heat dissipation from the subject 22 to beprocessed can be suppressed. As a result, it becomes possible to reducethe amount of heat that is required to heat the subject 22 to beprocessed and the controllability of the surface temperature of thesubject 22 to be processed is improved.

Next, a method of forming a thin film on the subject 22 to be processedby spray pyrolysis deposition using this film forming apparatus 21 willbe described.

Note that in the description given below, the description uses as anexample a case in which an ITO film is formed as a transparentconductive film on a substrate in the form of the subject 22 to beprocessed using the film forming apparatus 21 of the present embodiment,however, the present invention is not limited to this and can also beused to form a variety of thin films.

Firstly, a substrate whose surface is a clean surface is mounted on abase and this substrate and base are held together in a predeterminedposition.

A glass plate having a thickness of approximately between 0.3 mm and 5mm that is formed from a glass such as, for example, soda glass,heat-resistant glass, or quartz glass may be used for the substrate.

Once the substrate surface temperature has reached a predeterminedtemperature and stabilized, formation of the ITO film commences.

In the preparation chamber 220, the raw material solution for the ITOfilm is sprayed in preparation using a spraying device so as to form themist 23.

A solution containing components that form a conductive metallic oxidesuch as indium tin oxide (ITO) or the like as a result of being heatedmay be used as the raw material solution for the ITO film.

An aqueous solution or ethanol solution or ethanol-water mixturesolution containing 0.01 mol/L of tin chloride pentahydrate in anaqueous solution or ethanol solution or ethanol-water mixture solutioncontaining 0.2 mol/L of indium chloride tetrahydrate may be used as theraw material solution for the ITO film.

The mist 23 that is generated in the preparation chamber 220 istransported via the delivery path 221 to the film formation chamber 210,and is then sprayed from the nozzle (i.e., the discharge device 212)located in the top of the film formation chamber 210 towards the top ofthe substrate. As a result of this mist 23 adhering to the surface ofthe substrate that has been heated to a predetermined temperature, thesolvent in the mist is rapidly evaporated and any remaining soluteundergoes a rapid chemical reaction and changes into a conductivemetallic oxide such as ITO or the like. As a result, crystals that areformed by the conductive metallic oxide are rapidly generated on thesurface of the substrate and a transparent conductive film (i.e., an ITOfilm) is formed over a short period of time.

At this time, if the face velocity of the mist moving through the nozzleis designated such that the face velocity at the first portion 212 a,which is the mist intake side, is taken as V₁ and the face velocity atthe second portion 212 b, which is the mist discharge side, is taken asV₂, then V₂>1.5×V₁. The second portion 212 b that forms the dischargeaperture is slit-shaped.

The nozzle is further moved in a horizontal direction along one surfaceof the substrate. If this movement of the nozzle in a horizontaldirection is a reciprocating movement, then in the vicinity of the turnportion, the nozzle is moved in a direction in which it moves away fromthe surface of the substrate.

Once the formation of the ITO film is completed, it is cooled until thesubstrate temperature reaches a predetermined temperature and thesubstrate is then removed.

In this manner, a transparent conductive film that is made up of an ITOfilm is formed on the substrate.

In this film forming apparatus 21, if the face velocity of the mistmoving through the nozzle is designated such that the face velocity atthe first portion 212 a, which is the mist intake side, is taken as V₁and the face velocity at the second portion 212 b, which is the mistdischarge side, is taken as V₂, then V₂>1.5×V₁. By this means, theamount of mist sprayed over the entire surface of the subject 22 to beprocessed can be made uniform, and it is possible to improve the filmforming speed.

Furthermore, the nozzle is moved in a horizontal direction along onesurface of the subject 22 to be processed. If this movement of thenozzle in a horizontal direction is a reciprocating movement, then inthe vicinity of the turn portion, the nozzle is moved in a direction inwhich it moves away from the surface of the subject 22 to be processed.By this means, the amount of mist sprayed over the entire surface of thesubject 22 to be processed can be made uniform.

As a result, a transparent conductive film that is obtained in thismanner ends up having suppressed unevenness in the film thicknessdistribution over a large surface area. In addition, the in-planeuniformity of thin film characteristics such as, for example, sheetresistance and transmissivity is ensured, and a high quality product isobtained.

A description has been given above of film forming apparatuses ofexemplary embodiments of the present invention, however, the presentinvention is not limited to the above examples and can be appropriatelyaltered as is necessary.

EXAMPLES

Next, examples of the present invention will be described. These arespecific examples that make it possible for the present invention to bemore fully understood, however, the present invention is not limited tothese examples.

First Example

Firstly, in Example 1-1, an indium tin oxide (ITO) film is formed as atransparent conductive film. The solution that forms the raw materialfor this ITO film was prepared by dissolving 5.58 g of indium chloride(III) pentahydrate (InCl₃.5H₂O, molecular weight: 293.24) and 0.32 g oftin chloride (IV) pentahydrate (SnCl₄.5H₂O, molecular weight: 350.60) in100 ml of pure water serving as a solvent.

In Example 1-1, using the conditions shown in Table 1 below, liquid fineparticles that were generated by the liquid fine particle generatingdevice A were guided to the liquid fine particle guiding device B.Moreover, a bellows pipe made from vinyl chloride that can be elongatedor contracted was used for the delivery path of the liquid fine particleguiding device B that guides the liquid fine particles, and waterrepellency was ensured by treating the internal surface thereof with afluororesin.

TABLE 1 Item Parameter Starting raw material InCl₃•5H₂O, SnCl₄ SolventWater Temperature of liquid fine particles after generation 23° C.Temperature of liquid fine particles inside 23° C. delivery pathDelivery path exterior temperature 22° C. Proportion of droplets inliquid fine particles 1.5% by volume Flow rate of liquid fine particlesbeing transported 7,000 cm/min Length of delivery path 2.0 m

Moreover, in Example 1-1, using the conditions shown in Table 2 below,liquid fine particles that were guided by the liquid fine particleguiding device B were sprayed by the nozzle of the liquid fine particlespraying device C onto the glass substrate 110 serving as a subject tobe processed.

TABLE 2 Item Parameter Nozzle aperture size 60 φmm Liquid fine particletemperature (at nozzle aperture) 40° C. Flow rate of liquid fineparticles at nozzle aperture 15,000 cm/min Number of nozzles 4 Distancebetween nozzle and base material 20 mm Spraying time 15 min.

The volume distribution ratio relative to the particle diameter of theliquid fine particles generated on the basis of the above conditions wasthen measured and the droplet size distribution thereof was comparedwith that of droplets generated using a conventional apparatus in whichthe vapor supplied from the vapor supply component and the liquid thatis supplied from the liquid supply component are made to collide witheach other so that the raw material solution formed by the two ischanged into fine particles, and this raw material solution that hasbeen changed into fine particles is sprayed onto a base material bytwo-fluid spray nozzles. Note that a microscopic mist generatingapparatus manufactured by Atomax Co. Ltd. was used for the spray nozzlesin the present example. The results are shown in FIG. 6.

As is shown in FIG. 6, in a related art apparatus the droplet sizedistribution is between 9 μm and 160 μm, while in an apparatus that isbased on the present example the droplet size distribution is between 1μm and 60 μm so that the size of the droplet size distribution isreduced. As a result, droplets of 70 μm or larger can be removed and itbecomes possible to spray droplets that have a uniform particlediameter.

Moreover, in Example 1-1, a borosilicate glass plate having a size of500 mm×500 mm and a thickness of 2 mm was used for the base material,and the film thickness, sheet resistance, and transmissivity to visiblelight of an ITO film that was formed under the above describedconditions with the surface temperature of the glass substrate set to350° C. were each measured and compared with the same measurementresults from a related art apparatus. The results are shown in Table 3.

TABLE 3 Related Item Example 1-1 apparatus Art apparatus Surfacetemperature of glass 350° C. 350° C. substrate Film thicknessdistribution 610 to 650 nm 620 to 750 nm Sheet resistance distribution 3to 5 Ω/cm² 10 to 35 Ωcm² Transmissivity 80% 70%

From the results in Table 3, it can be understood that, in an apparatusthat is based on an exemplary embodiment of the present invention, it ispossible to contribute to the uniformity of the film thicknessdistribution and to the uniformity of the sheet resistance distribution,and to improve the film quality including transmissivity.

Moreover, in Example 1-1, using a borosilicate glass plate having a sizeof 500 mm×500 mm and a thickness of 2 mm for the base material, in orderto achieve a 500 mm×500 mm film formation, on the substrate side thisglass plate was driven ±150 mm in a direction taking a horizontaldirection as the X axis, and on the nozzle side was driven ±100 mm in adirection taking a horizontal direction that is orthogonal to the Xaxial direction on the substrate side as the Y axis. Accordingly, asubstrate-nozzle direction that is vertically orthogonal to both the Xaxial direction on the substrate side and the Y axial direction on thenozzle side is taken as a Z axial direction. The substrate was thenheated under the combined conditions (A)+(B) shown in Table 4 below.

TABLE 4 Item Parameter Type of coated film substrate Borosilicate glass(TEMPAX #8330) Coated film substrate size 500 × 500 × 2 mm Coated filmsubstrate surface 300 to 450° C. temperature Heating conditions (A) Heattransfer heating from substrate rear surface side + (B) Heat rayirradiation heating from substrate front surface (i.e., formed filmsurface) side Drive method (for film Drive in X axial direction ofsubstrate side formation over a (±150 mm) + drive in Y axial directionlarge surface area) of nozzle side (± 150 mm)

The film thickness distribution, sheet resistance distribution, andtransmissivity distribution in visible light of an ITO film that wasformed under the above described conditions were each measured andcompared with the same measurement results from a related art apparatus.The results are shown in Table 5. Note that the film formation time was15 minutes for both the apparatus of the present example and theconventional apparatus.

TABLE 5 Example 1-1 Related Item apparatus art apparatus Film thicknessdistribution 700 to 900 nm 200 to 1200 nm Sheet resistance distribution3 to 4 Ω/cm² 5 to 15 Ω/cm² Transmissivity distribution 75 to 83% 60 to82% (overall light ray transmissivity) Film formation time 15 min.

From the results shown in Table 5, it can be understood that in the samefilm formation time the film growth is more rapid and there is reducedfilm thickness distribution and sheet resistance distribution, and thereis also a significant improvement in the transmissivity characteristic.

It is thought that this is an effect of the fact that the in-planedistribution of the liquid fine particles that are sprayed from thenozzles have been made uniform, the fact that it has become possible tospray with the nozzles placed in close proximity to the substrate (i.e.,conventionally, 500 mm compared to 20 mm in Example 1-1), the fact thatit is possible to control the flow rate of the liquid fine particlesthat are sprayed from the nozzles, and the fact that it is possible tocontrol the temperature of the liquid fine particles until they reachthe substrate.

Example 2

Using a film forming apparatus of an exemplary embodiment of the presentinvention, an ITO film was formed as a transparent conductive film onthe substrate.

Firstly, a raw material solution was prepared in the manner describedbelow.

Preparation of ITO Raw Material Solution

The solution was prepared by dissolving chemical agents in a ratio of5.58 g/100 ml of indium chloride (III) tetrahydrate (InCl₃.4H₂O) and0.36 g of tin chloride (IV) pentahydrate (SnCl₄.5H₂O) in water.

Example 2-1 ITO Film Formation

A 500 mm×500 mm×2 mm^(t) borosilicate glass substrate (TEMPAX #8330) wasmounted on a supporting base and was heated from room temperature untilthe surface temperature reached 300 to 450° C. Note that the heating wasprovided by heat ray heating from an infrared lamp placed above the hoodin addition to heat transfer from a heating substrate placed below theglass substrate.

Once it was confirmed that the surface temperature of the substrate wasstable, ITO film formation was commenced.

The ITO raw material solution is sprayed in advance in a preparationchamber so as to form mist (i.e., liquid fine particles).

The mist conditions in the preparation chamber and on the delivery pathare shown in Table 6. Note that a bellows pipe made from vinyl chloridethat can be elongated or contracted is used for the delivery, and waterrepellency was ensured by providing a Teflon® coating on the internalwall thereof.

TABLE 6 Temperature of mist in preprocessing chamber 23° C. Temperatureof mist on delivery 23° C. Delivery path exterior temperature 22° C.Proportion of droplets in mist 1.5% by volume Flow rate of mist beingtransported 7,000 cm/min Length of delivery path 2.0 m

In the film formation chamber, four slit-shaped spray nozzles (having anozzle discharge aperture size of: 7×270 mm) were placed in the mannershown in FIG. 11 and the mist from the ITO raw material solution thathad been transported from the preparation chamber was sprayed onto thesubstrate. At this time, the temperature of the mist in the nozzledischarge apertures was 40° C., and the mist flow rate in the nozzledischarge apertures was 22500 cm/min.

Moreover, in order to achieve a 500 mm×500 mm film formation, thedistance between the spray nozzles and the glass substrate was set to 20mm, and any offset in the spraying density was prevented by imparting aswing on the substrate side of ±150 mm in the x direction, and a swingon the nozzle side of ±150 mm in the Y direction. The time required toform the Ito film was 15 minutes.

Comparative Example 2

Using circular cylinder-shaped nozzles an ITO film was formed on a glasssubstrate in the same manner as in the examples other than the nozzleswere driven elliptically as is shown in FIGS. 4A and 4B.

An ITO film was formed on a glass substrate in the above describedmanner.

A comparison of the characteristics of the substrates on which the ITOfilms were made in the example and the comparative example are shown inTable 7.

TABLE 7 Comparative Example 2-1 Example 2 Film thickness distribution[nm] 750 to 850 700 to 900 Sheet resistance distribution [Ω/cm²] 3.2 to3.9 2.6 to 4.4 Transmissivity distribution [%] 80 to 83 75 to 83(overall light ray transmissivity)

As evident from Table 7, in the example, the in-plane distribution ofthe sprayed mist quantity that was blown onto the substrate surface wasmade uniform. As a result, the film thickness and the thin filmcharacteristics distribution were made uniform.

Examples 2-2 to 2-4

In Examples 2-2 to 2-4, a comparison was made based on difference innozzle shape in slit type nozzles.

Other than the fact that nozzles having different shapes were used, ITOfilms were formed on glass substrates in the same manner as inExample 1. The three types of nozzle size and mist spray conditions thatwere used in Examples 2-2 to 2-4 are shown together in Table 8.

TABLE 8 Nozzle pipe inner diameter (D) [φcm] Example 2-2 Example 2-3Example 2-4 Nozzle discharge aperture 270 × 7 270 × 9 270 × 7 size (X,Y) [mm] Length of nozzle constricted 100 100 80 portion (B) [mm] Lengthof nozzle parallel 100 100 80 portion (C) [mm] Formula (2) relationshipYes No Yes Formula (3) relationship Yes Yes No Nozzle discharge aperture22500 17500 22500 flow rate [cm/min]

The air flow rate distribution at the discharge aperture when air wassupplied at 50,000 to 400,000 cm³/minute to each nozzle was measured.The results thereof are shown in Table 9.

TABLE 9 Flow rate distribution range [cm/min] Air flow rate [cm³/min]Example 2-2 Example 2-3 Example 2-4 50,000 ≦±5% ≦±11% ≦±12% 100,000 ≦±6%≦±10% ≦±15% 200,000 ≦±3% ≦±13% ≦±16% 40,000 ≦±7% ≦±12% ≦±12% 60,000 ≦±6%≦±11% ≦±11%

As evident from Table 9, it can be understood that the nozzles inExample 2-2 that satisfy the relationships of both Formula 2 and Formula3 have a small air flow rate distribution range and have excellent mistspray uniformity.

A comparison of the characteristics of the substrates on which the ITOfilms were formed in Examples 2-2 to 2-4 are shown in Table 10.

TABLE 10 Example Example Example 2-2 2-3 2-4 Film thickness distribution[nm] 750 to 850 710 to 880 700 to 850 Sheet resistance distribution[Ω/cm²] 3.2 to 3.9 2.8 to 4.2 2.6 to 4.3 Transmissivity distribution [%]80 to 83 76 to 83 77 to 82 (overall light ray transmissivity)

As evident from Table 10, in Example 2-2 in which nozzles that satisfythe relationships of both Formulae (1) and (2) were used, thedistribution range of the sheet resistance was decreased and thetransmissivity was improved. This is because the distribution range ofthe mist sprayed from the nozzle discharge apertures was decreased andthe film thickness distribution was made uniform.

INDUSTRIAL APPLICABILITY

The present invention can be applied to film forming apparatuses thatform a thin film such as a transparent conductive film or the like usingspray pyrolysis deposition.

Although the above exemplary embodiments of the present invention havebeen described, it will be understood by those skilled in the art thatthe present invention should not be limited to the described exemplaryembodiments, but that various changes and modifications can be madewithin the spirit and scope of the present invention. Accordingly, thescope of the present invention is not limited to the described range ofthe following claims.

1. A film forming apparatus, comprising: a supporting device on which asubject to be processed is mounted; and a discharging device that spraysa mist containing a raw material solution for the thin film towards asurface of the subject to be processed, wherein the discharge devicecomprises nozzles, each nozzle having a mist intake side and a mistdischarge side, and if a face velocity at the mist intake side is takenas V₁ and a face velocity at the mist discharge side is taken as V₂, aface velocity of the mist moving through the nozzles is V₂>1.5×V₁. 2.The film forming apparatus according to claim 1, wherein, in thenozzles, if a cross-sectional area of the mist intake side when seenfrom the discharge aperture side is taken as E₁ and a cross-sectionalarea of the mist discharge side is taken as E₂, E₁>1.5×E₂.
 3. The filmforming apparatus according to claim 1, wherein, in the nozzles, themist discharge side has a slit shape.
 4. The film forming apparatusaccording to claim 1, further comprising: a preparation chamber in whichmist is generated by spraying a raw material solution; and atransporting device defined by a via that enables the mist to move fromthe preparation chamber to the nozzles.
 5. The film forming apparatusaccording to claim 1, wherein, during film formation, the nozzles arepositionable in a horizontal direction relative to a surface of thesubject to be processed.
 6. The film forming apparatus according toclaim 5, wherein, during film formation, the nozzles are moveable in asubstantially horizontal reciprocating movement, wherein the nozzles areshifted in a direction in which they move toward and away from thesurface of the subject to be processed.